Java分析死鎖的方法

首先實現一個死鎖程序。

public class DeadLockSample extends Thread {
    private String first;
    private String second;

    public DeadLockSample(String name, String first, String second) {
        super(name);
        this.first = first;
        this.second = second;
    }

    @Override
    public void run() {
        synchronized (first) {
            System.out.println(this.getName() + " obtained: " + first);
            try {
                Thread.sleep(3000L);
                synchronized (second) {
                    System.out.println(this.getName() + " obtained: " + second);
                }
            } catch (InterruptedException e) {
                // do nothing
            }
        }
    }

    public static void main(String[] args) throws InterruptedException {
    /**
        ThreadMXBean mxBean = ManagementFactory.getThreadMXBean();
        Runnable dlCheck = new Runnable() {
            @Override
            public void run() {
                long[] threadIds = mxBean.findDeadlockedThreads();
                if (threadIds != null) {
                    ThreadInfo[] threadInfos = mxBean.getThreadInfo(threadIds);
                    System.out.println("Detected deadlock threads:");
                    for (ThreadInfo threadInfo : threadInfos) {
                        System.out.println(threadInfo.getThreadName());
                    }
                }
            }
        };
        ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(1);
        scheduledExecutorService.scheduleAtFixedRate(dlCheck, 5L, 10L, TimeUnit.SECONDS);
*/

        String lockA = "lockA";
        String lockB = "lockB";

        DeadLockSample t1 = new DeadLockSample("Thread1", lockA, lockB);
        DeadLockSample t2 = new DeadLockSample("Thread2", lockB, lockA);
        t1.start();
        t2.start();
        t1.join();
        t2.join();
    }
}

運行程序

分析

通過jps命令或者ps命令確定運行的進程ID

然後使用jstack命令獲取線程棧信息。

jstack 98485

可以看看這裏頭是否有BLOCKED狀態的線程，這樣很快就能定位出來。

我們需要區分線程狀態->查看等待目標->對比持有Monitor等持有的狀態。